1. Object of the Invention
The present invention refers, as the title indicates, to a pump for sea water desalination systems by reverse osmosis, of the type having two end chambers in which two pistons are housed which describe alternative movements, alternatively pumping sea water towards an reverse osmosis membrane pertaining to a desalination system, moreover, said system including a directional valve activated by a pilot valve which in turn is actuated by the own displacement of the pistons.
2. Background of the Invention
Currently, there are different pumps or pumping systems applicable to sea water desalination, which include a hydraulic cylinder, in which two pistons are housed and move alternatively to pump the sea water towards the osmosis membrane.
Generally, these systems include a directional valve permitting the pressure of the water rejected by the osmosis membrane to be harnessed, using it to collaborate in the piston cylinder and therefore increase the pressure of the water supplied to the membrane.
In this section, the U.S. Pat. No. 5,462,414, WO 98/22202, U.S. Pat. Nos. 4,367,140 and 4,793,153 describing similar systems should be mentioned.
To provoke inversion in the direction of the piston movement, said patents include a hydraulic circuit, always requiring the use of anti-return valves to permit their operation, moreover incorporating pilot and directional valves separated from the pump body, hence presenting different problems, on the one hand, the existence of a high number of outside conduits with the consequent risk of breakage and pressure losses, and on the other hand, making the anti-return valves useless due to the formation of saline deposits in the emplacement area thereof.
To solve the above problems, the pump for sea water desalination systems by reverse osmosis object of this invention, has been created having constructional features directed on the one hand, to permit operation without anti-return valves and on the other, to obtain a compact equipment with a very reduced number of external conduits.
Said pump, being of the type which have two end chambers in which the two pistons are housed, has the particularity that the pump body has a third chamber centrally arranged between the two end chambers, provided with an outside pressure intake, with two end mouths connected to the directional valve and an intermediate mouth connected to a water outlet conduit, said chamber housing a sliding block having a side cavity forming a closure with the wall of said third chamber. The sliding block carrying out, according to its position, the alternative opening of the end mouths connected to the directional valve and the interconnection by means of the lateral cavity of the other two mouths, simultaneously allowing the entry of pressure from the intermediate chamber to the directional valve and the guidance of water coming from the directional valve to the water outlet conduit.
This third chamber defined in the pump body, precisely constitutes the pilot valve of the directional valve.
The aforementioned sliding block, housed in the central chamber of the pump body internally has a hole for the passage of the piston shaft and an internal recess in which a thicknessing is housed with the possibility of longitudinal displacement, this thicknessing being entrusted with the displacement of the sliding block inside the third chamber of the pump when the pistons are next to the ends of their run.
According to the invention, the directional valve has a tubular body interlocked to the pump body and provided with two end compartments and two intermediate compartments, in which are housed, respectively, two pistons and two guides interlocked by a common shaft with possibility of simultaneous alternative displacement.
The end compartments of the directional valve are respectively connected to the end mouths of the pilot valve.
According to the invention, one of the intermediate compartments of the directional valve is connected to the reverse osmosis membrane intake and has two end mouths connected to the front areas of the end chambers of the pump body and a central mouth connected to the pressure intake and to the central chamber of the pump body. The guide arranged inside the mentioned intermediate component has a lateral cavity alternatively communicating the pressure intake with the front area of the end chambers of the pump body, permitting the alternative connection of the front areas of said end chambers of the pump with the mentioned intermediate compartment of the directional valve.
The other intermediate compartment of the directional valve is connected to the outlet of water outlet rejected by the reverse osmosis membrane and has two end mouths connected to the rear areas of the end chambers of the pump body and a central mouth connected to the intermediate mouth of the central chamber of the pump body and the water outlet to the exterior. The guide housed in this compartment has a lateral cavity, alternatively communicating the rear area of the end chambers of the pump body with the water outlet to the exterior, also alternatively permitting the connection of the rear areas of the end chambers of the pump body with said intermediate compartment of the directional valve.
The assembly of the directional valve over the pump body permits that the conduits relating it to the end chambers of the pump are internally defined and the guides housed inside the directional valve may perform, by means of the corresponding cavities, the interconnection in pairs of the mouths defined in the intermediate compartments of said directional valve, causing according to the direction of displacement of the pump pistons, the direction of the water under pressure towards the reverse osmosis membrane intake and the guidance of the water rejected by the osmosis membrane towards one of the rear areas of the end chambers of the pump.